Modern elevator systems often include distributed intelligence in the form of elevator car controllers, such as microprocessors.
In an elevator system the door of each elevator car is usually maintained open for a set period of time to allow passenger(s) to either board and/or deboard. The time period for which the system maintains the door open before a command to close is given is termed the "Door Dwell Time." An exemplary range of values for a fixed, pre-set dwell time is within a range of approximately four to six seconds.
In present elevator systems the amount of time an elevator car's doors are kept open is either hard-wired in the system, or is entered as constant numbers or as variables in electrically erasable, programmable read-only memory (EEPROM). This memory is coupled to a microprocessor controlling the door motion of the elevator cage. These selected parameters remain constant or static (unless changed on-site by human intervention during, for example, maintenance) for the life of the equipment.
The only Door Dwell Time difference that is standard in known types of conventional elevator systems is that hall calls and car calls are distinguished from one another. There is also an assumption that only one passenger will deboard for each car call and that only one passenger will board for each hall call. The preset dwell time for a hall call may be four seconds, while the preset dwell time for a car call is typically less than four seconds, since less time is typically needed to exit a car than to get to the car from an outside location.
However, a static or operationally fixed door dwell time may be insufficient for the traffic at hand, causing the doors to be prematurely commanded to close while passengers are still boarding and/or deboarding. This causes a "door reversal" to take place, when the closing doors make contact with one or more passengers, further wasting time and often slowing down the transferring traffic.
In commonly assigned U.S. Pat. No. 4,363,381, issued Dec. 14, 1982, entitled "Relative System Response Elevator Call Assignments" to J. Bittar there is described an elevator system in which hall calls registered at a plurality of landings are assigned to cars on the basis of a summation of relative system response factors for each car relative to each registered hall call. A discussion of door operation is made in columns 16 and 17.
In U.S. Pat. No. 4,193,478, issued Mar. 18, 1980, entitled Elevator Control System and Method", V. Keller et al. describe at column 8, line 61, to column 7, line 3, the operation of a door routine that is said to include options for different lengths of time or "door times" that elevator doors are allowed to stand open. The door times are selected depending upon what type of call has been answered or whether a direct signal to open the door has been initiated. The various programmable door times are said to be under software control. There is no indication in Keller that the door times are other than fixed, preprogrammed door times.
It is an object of this invention to provide an elevator system that employs a determination of Average Waiting Time to dynamically vary Door Dwell Time.